Rotary Pump Pressure Control Using Internal Overpressure
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Solution Overview
Problem
Rotary positive displacement pumps often produce output pressures that exceed the requirements of internal combustion engines, leading to energy wastage due to limitations in pressure relief valves and control mechanisms, especially at varying engine operating speeds.
Innovation Solution
A rotary positive displacement pump design that utilizes a higher pressure source within the pump to augment the force of a biasing spring, allowing for a control mechanism that reduces output pressure by using a piston and chamber system to manage the flow, enabling a closer match between pump output and engine requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed displacement pump with pressure relief valve is used, then the pump can meet engine lubrication requirements at low operating speeds, but the output pressure exceeds engine requirements at higher operating speeds causing energy waste
Solution Approach 1:
The invention employs a variable displacement pump mechanism where the pump's volumetric displacement can be dynamically adjusted based on operating conditions. A control piston responds to pressure differential forces (between outlet pressure and biasing spring pressure) to vary the pump displacement, enabling the system to adapt output pressure to match engine requirements across different operating speeds, thereby eliminating energy waste from excessive pressure while maintaining reliable lubrication supply.
Solution Approach 2:
The control mechanism incorporates feedback through a control piston that senses the outlet pressure of the pump. The pressure differential force acting on the control piston provides feedback about the current operating state, which automatically adjusts the pump displacement to maintain optimal pressure output. This closed-loop feedback system ensures the pump delivers exactly the pressure needed by the engine at any given operating speed, preventing energy waste.
2Loss of energy
If a variable displacement pump is used, then energy efficiency is improved by matching pump output to engine requirements, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The variable displacement control mechanism is designed to be self-actuating, using the pump's own outlet pressure and a biasing spring to automatically adjust pump displacement without requiring external control systems. The control piston responds autonomously to pressure differential forces, making the system self-regulating and eliminating the need for complex external sensors, actuators, or control electronics, thus maintaining simplicity while achieving energy efficiency.
Solution Approach 2:
The invention uses pneumatic/hydraulic principles by employing pressure differential forces acting on a control piston to vary pump displacement. The control piston is subjected to forces from outlet pressure on one side and biasing spring pressure on the other, creating a purely hydraulic control mechanism that is simple, reliable, and free from mechanical linkages or electronic controls, thereby achieving variable displacement without significant complexity increase.
3Reliability
If the pump output volume is increased to meet low speed requirements, then lubrication needs are satisfied at all operating speeds, but excessive pressure is generated at high operating speeds
Solution Approach 1:
The pump incorporates a variable displacement mechanism that dynamically adjusts volumetric output based on operating speed and pressure conditions. At low operating speeds, the pump maintains high displacement to ensure adequate lubrication supply volume. As operating speed increases, the control piston automatically reduces pump displacement, thereby maintaining reliable lubrication supply while preventing excessive pressure generation that would occur with fixed high displacement.
Solution Approach 2:
The invention changes the pump's volumetric displacement parameter in response to operating conditions. The control mechanism varies the pump displacement parameter based on the balance between outlet pressure and biasing spring pressure, allowing the system to maintain adequate lubrication supply volume across all speeds while adjusting pressure output to match engine requirements, thus avoiding excessive stress at high speeds.
Data Source
AI summary
A rotary positive displacement pump employs the higher pressure available at a region within the rotor chamber after the outlet port to augment the force of a biasing spring in a control system. A biasing spring with a lower spring force can thus be employed in the control system, resulting in a pump pressure output characteristic which can more closely match the operating speed varying working fluid requirements for devices supplied by the pump.